Using both features together can further reduce paper volume by 1/4!
To check the paper consumption, look at the total counter and the duplex counter.
The total counter counts all pages printed.
For one duplex page, the total counter goes up by 2.
For a duplex job of a three-page original, the total counter goes up by 3.
The duplex counter counts pages that have images on both sides.
For one duplex page, the duplex counter goes up by 1.
For a duplex job of a three-page original, the duplex counter will only increase by 1, even though two sheets are used.